De-restricting my Japanese import VFR750. Final step?

[stinkwheel]

Yey, de-restriction thread not a 'ped or 125. Mostly an account of what I've done so far. Bit of a question at the bottom.

As some of you will know, I bought a total frickin' lemon of a VFR750 a while back which had not only been flipped and cobbled back together but also turned out to be a Japanese import.

The thing about a Japanese import is that it is restricted to a maximum of 77bhp and 125mph... Damn.

The good bit is that it has a straight frame and clean, low mileage engine that can in no way have been over-stressed.

Some research showed the restriction on ths motor to be, as we're constantly telling 125 owners, physically engineered into several major parts of the bike. It's not just cutting a wire and knocking out a washer... well, cutting a wire is involved.

The first thing that I looked at (and what alerted me to it being an import) is the top speed restrictor. This is an optical sensor in the back of the speedo which cuts the spark to the rear cylinders if a duplicate speedo needle on the inside hits 125mph. This can be removed, but not by cutting it. You need to make a voltage divider to feed lies to the CDI.
Discussed in this thread

I later found that the CDI from my UK spec 3rd Gen VFR750 plugs right in. There is apparently a difference in the advance curve.

Yeah. So far so good but it would also appear the cams are restricted. UK spec ones are a different part number and much pointier. Thankfully it turns out there is virtually no demand for scrap VFR750 cylinder heads. Got a complete pair for £75 (including cams and followers). A day in the workshop and I'd fitted the UK spec cams and shimmed up the valves. Remarkably, I only needed two shims! That's some hell of an engineering tolerances.

I fitted the K&N filter and original 90's micron end-can from my old VFR and we come down to the final point. Carbs.

I've been running this bike, a second generation, on the already dynojetted flatslides off my old third gen bike. It's nowhere near as quick but it ought to be, I've replaced all the other stuff where it differs.

I've also noticed the tank range is really shitty. I was getting 160 miles from a tank on my old one, I'm lucky to get 130 on this. It was brought home to me when I used nearly as much fuel on a run over the Tomintoul road as my mates blueprinted, 150bhp oil-boiler GSXR1100...

So I need to address the carbs. I could buy a set of UK spec ones off ebay but chances are they'll be well worn by this point. Throttle slides are pure unobtanium, needles are expensive.

Thing is, I have a set of proper carbs right here. The low mileage, Japanese spec. ones it came with. I've compared the spec with the European version. They are the same general type of Kehin carb. A VDJ4A. Choke diameter is the same, slide and diaphragm is the same, spring is the same.

The carb body itself has a different part number. Main jet is different. Throttle needle is different. Mixture screw insert is different. Slow runing jet is the same.

My plan is to get a stange 1 dynojet kit for it. It's appropriate for the filter and pipe I have. This should contain a set of full power main jets, needles and possibly springs.

What I can't change are the mixture screw insert (unobtanium) and the carb bodies. I'm pretty sure the mixture screw will only make a very minimal difference and only at small throttle openings, it might even make it more handleable in town. I should also be ok at full-bore-roar, correct slide cutaway, jet diameter and needle profile.

It's the carb bodies I'm concerned about. There are other jets in there which form part of the carb itself and fill in holes in the rev range. Probably in the upper third of throttle openings. I don't know if these are the same or different.


TL;DR
Does anyone know how specific Kehin carb part numbers are? Is every VDJ4A internally the same apart from the removable fittings? Or do they vary from application to application?

I suspect the answer will be suck it and see. I'm hoping worst case, it's a tad on the softy side in the midrange then comes in with a kick up the arse as it goes onto the main jet.

Or am I going to assplode and die?
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[kramdra]

[stinkwheel]

I don't think they're restricted. I think they're plain wrong for this engine varient. It's burning a lot of fuel and not going as fast as I think it should.

Only other thing I can think that could be missing/holding it back other than carbs is ignition advance at the level of the flywheel/pickups.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[kramdra]

You've not said how it runs on the standard, jap carbs?

[MCN]